2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 @DsMonad@: monadery used in desugaring
10 DsM, mappM, mapAndUnzipM,
11 initDs, initDsTc, returnDs, thenDs, listDs, fixDs, mapAndUnzipDs,
14 newTyVarsDs, newLocalName,
15 duplicateLocalDs, newSysLocalDs, newSysLocalsDs, newUniqueId,
17 getSrcSpanDs, putSrcSpanDs,
20 UniqSupply, newUniqueSupply,
21 getDOptsDs, getGhcModeDs, doptDs,
22 dsLookupGlobal, dsLookupGlobalId, dsLookupTyCon, dsLookupDataCon,
24 DsMetaEnv, DsMetaVal(..), dsLookupMetaEnv, dsExtendMetaEnv,
28 DsWarning, warnDs, failWithDs,
32 EquationInfo(..), MatchResult(..), DsWrapper, idDsWrapper,
36 #include "HsVersions.h"
68 %************************************************************************
70 Data types for the desugarer
72 %************************************************************************
76 = DsMatchContext (HsMatchContext Name) SrcSpan
81 = EqnInfo { eqn_pats :: [Pat Id], -- The patterns for an eqn
82 eqn_rhs :: MatchResult } -- What to do after match
84 type DsWrapper = CoreExpr -> CoreExpr
87 -- The semantics of (match vs (EqnInfo wrap pats rhs)) is the MatchResult
88 -- \fail. wrap (case vs of { pats -> rhs fail })
89 -- where vs are not bound by wrap
92 -- A MatchResult is an expression with a hole in it
95 CanItFail -- Tells whether the failure expression is used
96 (CoreExpr -> DsM CoreExpr)
97 -- Takes a expression to plug in at the
98 -- failure point(s). The expression should
101 data CanItFail = CanFail | CantFail
103 orFail CantFail CantFail = CantFail
108 %************************************************************************
112 %************************************************************************
114 Now the mondo monad magic (yes, @DsM@ is a silly name)---carry around
115 a @UniqueSupply@ and some annotations, which
116 presumably include source-file location information:
118 type DsM result = TcRnIf DsGblEnv DsLclEnv result
120 -- Compatibility functions
127 mapAndUnzipDs = mapAndUnzipM
130 type DsWarning = (SrcSpan, SDoc)
131 -- Not quite the same as a WarnMsg, we have an SDoc here
132 -- and we'll do the print_unqual stuff later on to turn it
135 data DsGblEnv = DsGblEnv {
136 ds_mod :: Module, -- For SCC profiling
137 ds_unqual :: PrintUnqualified,
138 ds_msgs :: IORef Messages, -- Warning messages
139 ds_if_env :: (IfGblEnv, IfLclEnv), -- Used for looking up global,
140 -- possibly-imported things
141 ds_bkptSites :: IORef SiteMap -- Inserted Breakpoints sites
144 data DsLclEnv = DsLclEnv {
145 ds_meta :: DsMetaEnv, -- Template Haskell bindings
146 ds_loc :: SrcSpan -- to put in pattern-matching error msgs
149 -- Inside [| |] brackets, the desugarer looks
150 -- up variables in the DsMetaEnv
151 type DsMetaEnv = NameEnv DsMetaVal
154 = Bound Id -- Bound by a pattern inside the [| |].
155 -- Will be dynamically alpha renamed.
156 -- The Id has type THSyntax.Var
158 | Splice (HsExpr Id) -- These bindings are introduced by
159 -- the PendingSplices on a HsBracketOut
162 -> Module -> GlobalRdrEnv -> TypeEnv
165 -- Print errors and warnings, if any arise
167 initDs hsc_env mod rdr_env type_env thing_inside
168 = do { msg_var <- newIORef (emptyBag, emptyBag)
169 ; let (ds_gbl_env, ds_lcl_env) = mkDsEnvs mod rdr_env type_env msg_var
171 ; either_res <- initTcRnIf 'd' hsc_env ds_gbl_env ds_lcl_env $
172 tryM thing_inside -- Catch exceptions (= errors during desugaring)
174 -- Display any errors and warnings
175 -- Note: if -Werror is used, we don't signal an error here.
176 ; let dflags = hsc_dflags hsc_env
177 ; msgs <- readIORef msg_var
178 ; printErrorsAndWarnings dflags msgs
180 ; let final_res | errorsFound dflags msgs = Nothing
181 | otherwise = case either_res of
182 Right res -> Just res
183 Left exn -> pprPanic "initDs" (text (show exn))
184 -- The (Left exn) case happens when the thing_inside throws
185 -- a UserError exception. Then it should have put an error
186 -- message in msg_var, so we just discard the exception
190 initDsTc :: DsM a -> TcM a
191 initDsTc thing_inside
192 = do { this_mod <- getModule
193 ; tcg_env <- getGblEnv
194 ; msg_var <- getErrsVar
195 ; let type_env = tcg_type_env tcg_env
196 rdr_env = tcg_rdr_env tcg_env
197 ; setEnvs (mkDsEnvs this_mod rdr_env type_env msg_var) thing_inside }
199 mkDsEnvs :: Module -> GlobalRdrEnv -> TypeEnv
200 -> IORef Messages -> (DsGblEnv, DsLclEnv)
201 mkDsEnvs mod rdr_env type_env msg_var
204 if_genv = IfGblEnv { if_rec_types = Just (mod, return type_env) }
205 if_lenv = mkIfLclEnv mod (ptext SLIT("GHC error in desugarer lookup in") <+> ppr mod)
206 gbl_env = DsGblEnv { ds_mod = mod,
207 ds_if_env = (if_genv, if_lenv),
208 ds_unqual = mkPrintUnqualified rdr_env,
210 lcl_env = DsLclEnv { ds_meta = emptyNameEnv,
214 %************************************************************************
216 Operations in the monad
218 %************************************************************************
220 And all this mysterious stuff is so we can occasionally reach out and
221 grab one or more names. @newLocalDs@ isn't exported---exported
222 functions are defined with it. The difference in name-strings makes
223 it easier to read debugging output.
226 -- Make a new Id with the same print name, but different type, and new unique
227 newUniqueId :: Name -> Type -> DsM Id
229 = newUnique `thenDs` \ uniq ->
230 returnDs (mkSysLocal (occNameFS (nameOccName id)) uniq ty)
232 duplicateLocalDs :: Id -> DsM Id
233 duplicateLocalDs old_local
234 = newUnique `thenDs` \ uniq ->
235 returnDs (setIdUnique old_local uniq)
237 newSysLocalDs, newFailLocalDs :: Type -> DsM Id
239 = newUnique `thenDs` \ uniq ->
240 returnDs (mkSysLocal FSLIT("ds") uniq ty)
242 newSysLocalsDs tys = mappM newSysLocalDs tys
245 = newUnique `thenDs` \ uniq ->
246 returnDs (mkSysLocal FSLIT("fail") uniq ty)
247 -- The UserLocal bit just helps make the code a little clearer
251 newTyVarsDs :: [TyVar] -> DsM [TyVar]
252 newTyVarsDs tyvar_tmpls
253 = newUniqueSupply `thenDs` \ uniqs ->
254 returnDs (zipWith setTyVarUnique tyvar_tmpls (uniqsFromSupply uniqs))
257 We can also reach out and either set/grab location information from
258 the @SrcSpan@ being carried around.
261 getDOptsDs :: DsM DynFlags
262 getDOptsDs = getDOpts
264 doptDs :: DynFlag -> TcRnIf gbl lcl Bool
267 getGhcModeDs :: DsM GhcMode
268 getGhcModeDs = getDOptsDs >>= return . ghcMode
270 getModuleDs :: DsM Module
271 getModuleDs = do { env <- getGblEnv; return (ds_mod env) }
273 getSrcSpanDs :: DsM SrcSpan
274 getSrcSpanDs = do { env <- getLclEnv; return (ds_loc env) }
276 putSrcSpanDs :: SrcSpan -> DsM a -> DsM a
277 putSrcSpanDs new_loc thing_inside = updLclEnv (\ env -> env {ds_loc = new_loc}) thing_inside
279 warnDs :: SDoc -> DsM ()
280 warnDs warn = do { env <- getGblEnv
281 ; loc <- getSrcSpanDs
282 ; let msg = mkWarnMsg loc (ds_unqual env)
283 (ptext SLIT("Warning:") <+> warn)
284 ; updMutVar (ds_msgs env) (\ (w,e) -> (w `snocBag` msg, e)) }
287 failWithDs :: SDoc -> DsM a
289 = do { env <- getGblEnv
290 ; loc <- getSrcSpanDs
291 ; let msg = mkErrMsg loc (ds_unqual env) err
292 ; updMutVar (ds_msgs env) (\ (w,e) -> (w, e `snocBag` msg))
298 dsLookupGlobal :: Name -> DsM TyThing
299 -- Very like TcEnv.tcLookupGlobal
301 = do { env <- getGblEnv
302 ; setEnvs (ds_if_env env)
303 (tcIfaceGlobal name) }
305 dsLookupGlobalId :: Name -> DsM Id
306 dsLookupGlobalId name
307 = dsLookupGlobal name `thenDs` \ thing ->
308 returnDs (tyThingId thing)
310 dsLookupTyCon :: Name -> DsM TyCon
312 = dsLookupGlobal name `thenDs` \ thing ->
313 returnDs (tyThingTyCon thing)
315 dsLookupDataCon :: Name -> DsM DataCon
317 = dsLookupGlobal name `thenDs` \ thing ->
318 returnDs (tyThingDataCon thing)
322 dsLookupMetaEnv :: Name -> DsM (Maybe DsMetaVal)
323 dsLookupMetaEnv name = do { env <- getLclEnv; return (lookupNameEnv (ds_meta env) name) }
325 dsExtendMetaEnv :: DsMetaEnv -> DsM a -> DsM a
326 dsExtendMetaEnv menv thing_inside
327 = updLclEnv (\env -> env { ds_meta = ds_meta env `plusNameEnv` menv }) thing_inside
332 getBkptSitesDs :: DsM (IORef SiteMap)
333 getBkptSitesDs = do { env <- getGblEnv; return (ds_bkptSites env) }